The invention generally relates to an implantable injection body for time-dependent, dosable, long-term injection of a medication into a living being. More specifically, the invention relates to an implantable injection body wherein medication to be long-term, time-dependent, dosably injected into a living being is stored in an implantable medication dosing device and is supplied to the injection body via a programmable pump arrangement, the injection body being provided with a plurality of medication discharge openings that follow one another in the flow direction of the medication and that are arranged in spaced apart construction.
In many instances, liquid medications must be supplied to a living being over a relatively long period of time. Medication dosing devices are currently available for such long-term applications, for example, as required in the case of diabetics. These devices administer a liquid medication, for example, insulin, to the patient in programmable doses and at programmable intervals.
External and/or implantable micro-dosing devices can be involved. In either instance, the medication is delivered to the patient via an implantable injection body. This delivery can occur in various ways, namely subcutaneously, intraperitoneally, or intravenously.
In the case of subcutaneous delivery, a catheter hose is subcutaneously laid between the discharge of the medication pump and the injection location, the distal end of this catheter hose being constructed as an injection needle made of metal or plastic. In the case of intravenous injection, the distal end of the catheter can be a blunt end or can comprise a specific tip that is provided with a discharge opening for the medication. An implantable injection body in catheter form is disclosed in West German patent application DE-A-38 05 508/2, having corresponding European patent 330012 and U.S. patent application Ser. No. 310,617, filed Feb. 15, 1985, now U.S. Pat. No. 4,976,703, the teachings of which are fully incorporated herein by reference.
As a consequence of reactions of the body of the living being to foreign bodies, such injection bodies are attacked within defined time spans. Generally, a connective tissue agglomerates to the injection body beginning from the distal end and continuing backwards. Over and above this, body cells, macro-molecules and tissue particles can penetrate into the medication discharge openings and can agglomerate to the inside walls of the injection body. The discharge opening is ultimately closed due to these body reactions of the living being.
In order to delay this process, the catheter construction of DE-A-38 05 508/2 is provided with a discharge opening that is constructed displaced from the tip in the distal direction. In this construction, moreover, through slots that serve as emergency openings can be distally provided in displaced relation from the main discharge opening, these emergency openings spreading under the pressure of the medication when the main discharge opening is blocked. Plastic material can be employed to make the catheter, thus enabling an emergency discharge. Since the adhesion of growths is particularly dependent on the surface roughness of the injection body and on the surface design thereof, such injection bodies have been coated with especially smooth, tissue-compatible protective layers and the geometrical shape of the injection body has been selected such that corners and edges are avoided.
All of these measures are in fact suitable for retarding the medication discharge opening from closure from being grown shut or blocked, but cannot prevent such closure. The bypass of the medication discharge to emergency openings also does not necessarily lead to a malfunction-free continuation of the injection process, but at most prevents an immediate interruption of the medication delivery. Due to the higher liquid pressure in the overall medication line, as a consequence of the force needed to supply the medication from the closed or closing slot-shaped emergency openings, the energy consumption of the pump is increased. This increased pump energy consumption can lead to a shortening of the useful life of the energy source.
Over and above the foregoing, the slots of the emergency discharge openings have relatively sharp edges. The sharp edges in turn can lead to an accelerated agglomeration of tissue particles and, thus, to a relatively short service life of the openings.
The provision of a plurality of simultaneously functioning openings also is disadvantageous because the throughput rate of the medication with reference to every individual opening decreases in accordance with the number of openings. As experience has taught, the service life of an opening is roughly proportional to the throughput rate of the medication. The service life of such an opening is thus greater the higher the throughput rate. This results in contradictory design considerations: the desire to reduce the number of openings to increase the throughput rates per opening, and the desire to increase the number of openings to provide for more bypass openings. At any rate, it has not been possible to achieve services lives for known catheters for the injection of medications that even approximate the useful life of the dosing device.